Slice conveyor furnace

ABSTRACT

In a continuous flow asher furnace, an organic material removing environment is continuously maintained in a furnace chamber. Integrated circuit slices are continuously transported through the environment by lead screws positioned within the chamber. Disks mounted at opposite ends of the chamber are periodically indexed to rotate individual slices into and out of the furnace.

United States Patent Wells Feb. 1, 1972 [54] SLICE CONVEYOR FURNACE 2,391,339 12/1945 Pearson ..263/6 [72] Inventor: Wallace Ogden Wells, Garland, Tex. git; [73] Assignee: Texas Instruments Incorporated, Dallas, T I l I n Primary ExaminerCharles J. Myhre Attorne Melvin Shar John E. Vand' riff Hem T. Olsen 22 F1 d. A .1 1969 Y Y 1 1 sr '5 and MichaelA. Sileo, Jr. [21] App .No.: 6,85

[57] ABSTRACT U-S- Cl- ..263/6R [n a continuous flow asher furnace an organic material [51] '3" 9/14 F 27d 9 removing environment is continuously maintained in a fur- [58] Fleld Search "263/6, 219/ 3 nace chamber. integrated circuit slices are continuously trans- 98/ ported through the environment by lead screws positioned R f r n 8 Ct d within the chamber. Disks mounted at opposite ends of the e e e c 8 le chamber are periodically indexed to rotate individual slices UNITED STATES PATENTS into and out of the furnace.

2,338,055 12/ 1943 Pearson et al. 198/82 7 Claims, 2 Drawing Figures 60 /2 (i 2 7 72 l6 1 34 3 4 68 34 70 7a 34 1 4 I// 7 /V' 6O 52.. 5o /,7a 54 56 2 50 //f 4 86 i i 44 26 E i6 0 c g a i I 1 a I a as i i i 2 3 a 3 c: v g 3 a4 0 n 3 8 o o o n c n c D c I) c D I 3 14 2 6 as r e 1\ gas -24 22- 48 9s 94 4'9 \90 6 311 PATENIEBFEB rm? 3.638.927, SHEEI NF 2 PATENTEUFEB 1:972 3.638.927

sum 2 or 2 INVENTOR WALLACE OGDEN WELLS AT TOR N E Y N 9 LL SLICE CONVEYOR FURNACE During the fabrication of integrated circuit slices and similar products, various photoresist compounds, etching solutions and other organic materials are applied to the slices. Although these materials are frequently at least partially removed from the slices during subsequent operations, it is often desirable to remove all organic materials from the slices at the end of the slice forming process. Typically, this operation is performed in a device known as an asher furnace.

In an asher furnace, slices are heated in a controlled atmosphere that contains ionized oxygen. This procedure transforms all organic materials on the slices into carbon dioxide and water vapor. These gases are removed from the furnace so that at the end of the process, the slices are free of both organic materials and combustion byproducts.

In the past, most asher furnaces have been batch-processtype devices. Typically, a quantity of slices is loaded into a chamber and the chamber is sealed. The controlled atmosphere is then established in the chamber and the slices are heated. When all organic materials have been removed from the slices, the chamber'is opened to permit removal of the treated slices and loading of a new batch of untreated slices.

Several problems result from the use of batch-type asher furnaces. For example, because it is difficult to maintain uniform temperature and atmospheric conditions throughout a furnace chamber, the slices comprising an individual batch are not all processed in the same manner. Also, because it is almost impossible to expose different batches of slices to the same temperature and atmosphere conditions, differences between slices processed in different batches are common.

This invention relates to a continuous flow asher furnace in which all slices are processed exactly alike. Each slice is transported through a chamber in which the temperature and atmosphere are continuously controlled. All slices are transported over the same path at the same rate. By this means, slice-to-slice and batch-to-batch variations between the slices are eliminated.

In accordance with the preferred embodiment, this invention comprises a continuous flow asher furnace in which an organic material removing environment is continuously maintained and in which workpieces are transported through the environment on an individual basis. Preferably, the environment is maintained in a sealed chamber and workpieces are transported through the environment by lead screws. Individual workpieces are rotated into and out of the furnace by disks mounted at opposite ends of the chamber.

A more complete understanding of the invention may be had by referring to the following detailed description when considered in conjunction with the drawings, wherein:

FIG. 1 is a sectional view of an asher furnace employing the invention, and

FIG. 2 is a top view of the device shown in FIG. 1 in which certain parts have been omitted more clearly to illustrate certain features of the invention.

' Referring now to the drawings, and particularly to FIG. 1 thereof, a continuous flow asher furnace l employing the invention is shown. The furnace includes a frame comprising an upper frame assembly 12 and a lower frame assembly 14. The upper frame assembly 12 includes .an outer plate 16, an intermediate plate 18, and an inner plate 20. Similarly, the lower frame assembly 14 includes an outer plate 22 and an inner plate 24. Suitable support members (not shown) extend between the assemblies 12 and 14.

A furnace chamber 26 is positioned between the upper frame assembly 12 and the lower frame assembly 14. The chamber 26 includes a quartz tube 28 which extends between thepair of sealing members 30 and 32 mounted in the plate and the plate 24, respectively. The ends of the chamber 26 are sealed by a plurality of sealing members 34 mounted in the several components of the frame assemblies 12 and 14.

A pair of ports 36 and 38 extend into the upper end and lower end of the quartz tube 28, respectively, for use in controlling the atmosphere within the chamber 26. The interior of the chamber 26 is heated by an induction coil 40 positioned around the exterior of the tube 28. The coil 40 is powered by a suitable source of induction heating power (not shown).

In the operation of the asher furnace 10, an organic material removing environment is continuously maintained within the chamber 26 by continuously operating the induction coil 40, by continuously directing a suitable atmosphere through the port 36 and bycontinuously removing combustion byproducts through the port 38. Preferably, the environment in the chamber 26 includes ionized oxygen. Integrated circuit slices are continuously transported through the environment by a slice transporting mechanism 44. The mechanism 44 operates to expose the slices to the organic material removing environment in the chamber 26 for a sufficient period of time to remove all organic materials from the slices.

The slice transporting mechanism 44 includes-a plurality of lead screws 46 that are positioned in a circular array within the quartz tube 48. Each lead screw 46 is supported in the plate 24 of the lower frame assembly 14 by a bearing 48. Each lead screw 46 is driven through a spur gear 50 secured to its upper end.

The spur gears 50 are mounted in mesh with a ring gear 52. The gear 52 is rotatably supported in the upper frame assembly 12 by a pair of ring-shaped polytetrafluoroethylene bearings 54 and is mounted in mesh with a spur gear 56. The gear 56 is rotatably supported in the plate 20 by a bearing 58 and is secured to a shaft 60 which is in turn rotated by a suitable motor (not shown). The spur gear 56, the ring gear 52, and the spur gears 50 are so constructed that each lead screw 46 makes one complete revolution about its axis for each complete revolution of the shaft 60.

The slice transporting mechanism 44 further includes an upper disk-shaped member 62 and a lower disk-shaped member 64 which moves slices into and out of the chamber 26, respectively. The upper disk-shaped member 62 includes a hub portion 68 and a flange portion 66 having a thickness slightly greater than the thickness of the slices operated upon by the furnace 10. The flange portion 66 has a pair of slice receiving apertures 70 formed in it. The hub portion 68 is secured to a drive hub 72 which is rotatably supported in the plate 16 of the upper frame assembly 12 by a pair of bearings In use, the hub 72 is periodically rotated through half revolution increments by a suitable indexing mechanism, such as a Geneva or the like. Rotation of the hub 72 rotates the apertures 70 of the member 62 between a slice receiving hold 76 formed in the plate 16 and a hole 78 formed in the plate 18 of the frame assembly 12. As the member 62 rotates, integrated circuit slices are moved in the apertures 70 between the hole 76 and the hole 78 as is best shown in FIG. 2, the hole 78 is coaxial with the quartz tube 28 and a circle extending through the axis of all the lead screws 46. Accordingly, slices transferred into alignment with the hole 78 by the member 62' immediately fall into engagement with the lead screws 46 for transportation thereby through the chamber 26.

Referring again to FIG. 1, the hub 72 is also secured to a spur gear 80. The gear 80 is mounted in mesh with a gear 82 which has the same number of teeth as the gear 80. The gear is secured to a shaft 84 which is rotatably supported in the plate 20 of the upper frame assembly 14 by a pair of bearings 86. The shaft extends through the plate 24 of the lower frame assembly l6 and is rotatably supported therein by a bearing 88.

The shaft 84 is mounted in driving engagement with the lower disk-shaped member 64. The member 64 is similar to the member 62 in that it includes a hub portion which is drivenly connected to the shaft 84 and an outer flange portion 92 having thickness slightly greater than the thickness of the slices operated upon by the furnace 10. The member 64 includes a pair of slice receiving apertures 94 and operates to rotate the apertures 94 between a hole 96 formed in the plate 24 and a hole 98 formed in the plate 22 of the lower frame assembly 16. As is shown in FIG. 2, the hole 96 is coaxial with the center line of the tube 28 and the center of a circle extending through the axes of all lead screws 46. Accordingly, slices which have been transported through the furnace by the lead screws 46 fall through the hole 96 in the plate 26 into an aperture 94 in the member 64. The member 64 rotates the slices in the apertures 94 into alignment with the hole 98 formed in the plate 24, whereupon the slices fall from the furnace 10.

The furnace 10 is intended for use as part of a continuous flow integrated circuit slice processing system. In such a system, slices are continuously deposited in the hole 76 by a slice delivery mechanism such as a track or the like. Preferably, the slice delivery mechanism deposits one slice in the hole 76 for each revolution of the shaft 60. In such a case, the upper disk-shaped member 62 is indexed through a half revolution for each complete revolution of the lead screws 46 and operates to position a slice in engagement with each turn of the lead screws.

Similarly, slices discharged from the furnace 10 through the hole 98 are received by a slice removing mechanism such as an air track or the like. The slice removing mechanism is also coordinated with the operation of the furnace 10 so that slices are transported from the furnace to the next step in the slice processing system in timed sequence.

The asher furnace illustrated in the drawing differs from prior asher furnaces principally in that it is a continuous flow device. As opposed to batch-process-type furnaces, the environment in the chamber of the furnace according to the present invention is brought into a steady-state condition of temperature and atmosphere before the first slice is introduced into the chamber and is thereafter continuously maintained. The slice transporting mechanism of the furnace moves all slices along the same path and positions each slice within the furnace chamber for the same period of time. Thus, each slice is acted upon by the furnace in exactly the same manner. Because all slices are treated alike, the slice-to-slice and batch-to-batch variations that commonly occur in the batch processing operations are completely eliminated.

Another important advantage resulting from the use of the furnace illustrated in the drawings is that slices are operated upon by the furnace in sequence. That is, slices are discharged from the furnace in exactly the same order that they were introduced. This feature is very important in a continuous flow slice processing system because it permits exact control over the entire process. Furthermore, sequential operation permits both simplified tracing of the effects of engineering changes and more rapid correction of system failures.

Although only one embodiment of the invention is illustrated in the drawings and described herein, it will be understood that the invention is not limited to the embodiment disclosed but is capable of rearrangement, modification and substitution of parts and elements without departing from the spirit of the invention.

What is claimed is:

1. An asher furnace comprising:

a furnace chamber having workpiece admitting and discharging openings extending into it;

means mounted in the chamber for transporting workpieces between the openings, and;

means for moving workpieces into and out of alignment with the admitting and discharging openings, wherein the workpiece moving means includes a disk mounted at one end of the chamber for rotation between a slice receiving point and the admitting opening and a disk mounted at the other end of the chamber for rotation between a slice releasing point and the discharging opening.

2. The asher furnace according to claim 1 wherein the transporting means maintains the workpieces in sequence as they are transported through the environment.

3. The furnace according to claim 1 further including means for rotating the disks in synchronism so that one workpiece is discharged from the chamber for each workpiece admitted thereto.

4. The furnace according to claim 1 whereln said furnace chamber includes means for maintaining a preselected environment within said chamber.

5. In a furnace, a slice handling system comprising a. a plurality of lead screws positioned at space points around an axis; and

b. means for delivering individual slices to a point on the axis at one end of the screws and for removing individual slices from a point on the axis at the other end of the screws wherein the delivery and removing means includes a pair of members having slice receiving openings formed in them and means for bringing the openings in the members into alignment with the points.

6. The furnace according to claim 5 wherein the delivery and removing means moves one workpiece out of engagement with the lead screws for each workpiece moved into engagement with the lead screws.

7. in a furnace, a slice handling system comprising:

a. a plurality of lead screws positioned at space points around an axis; and

b. means for delivering individual slices to a point on the axis at one end of the screws and for removing individual slices from a point on the axis at the other end of the screws wherein the delivery and removing means includes a pair of disk-shaped members having slice receiving apertures formed in them and means for rotatably supporting the disk-shaped members at opposite ends of the screws. 

1. An asher furnace comprising: a furnace chamber having workpiece admitting and discharging openings extending into it; means mounted in the chamber for transporting workpieces between the openings, and; means for moving workpieces into and out of alignment with the admitting and discharging openings, wherein the workpiece moving means includes a disk mounted at one end of the chamber for rotation between a slice receiving point and the admitting opening and a disk mounted at the other end of the chamber for rotation between a slice releasing point and the discharging opening.
 2. The asher furnace according to claim 1 wherein the transporting means maintains the workpieces in sequence as they are transported through the environment.
 3. The furnace according to claim 1 further including means for rotating the disks in synchronism so that one workpiece is discharged from the chamber for each workpiece admitted thereto.
 4. The furnace according to claim 1 wherein said furnace chamber includes means for maintaining a preselected environment within said chamber.
 5. In a furnace, a slice handling system comprising a. a plurality of lead screws positioned at space points around an axis; and b. means for delivering individual slices to a point on the axis at one end of the screws and for removing individual slices from a point on the axis at the other end of the screws wherein the delivery and removing means includes a pair of members having slice receiving openings formed in them and means for bringing the openings in the members into alignment with the points.
 6. The furnace according to claim 5 wherein the delivery and removing means moves one workpiece out of engagement with the lead screws for each workpiece moved into engagement with the lead screws.
 7. In a furnace, a slice handling system comprising: a. a plurality of lead screws positioned at space points around an axis; and b. means for delivering individual slices to a point on the axis at one end of the screws and for removing individual slices from a point on the axis at the other end of the screws wherein the delivery and removing means includes a pair of disk-shaped members having slice receiving apertures formed in them and means for rotatably supporting the disk-shaped members at opposite ends of the screws. 